Automatic telephone trunking-switch and system therefor.



W. L. CAMPBELL.

AUTOMATIC TELEPHONE TRUNKING SWITCH AND SYSTEM THEHIFOH APPLICATION FILED .IULY 9| 1907r Patented Apr. 3, 1917.

3 SHEETS--SHEET I LIQ.

w. L.. CAMPBELL. AUTOMA'HC TELEPHONE TRUNKING SWITCH AND SYSTEM THEREFOR.

y APPLICATION FILED JULY 9| 1,907- 1,221,287, s Pntented Apr. 3, 1917.`

s sains-.SHEET 2.'

W. L. CAMPBELL. AUTOMATIC TELEPHONE TRUNKING SWICH AND SY'STEMTHEREFORf AFPLICAUON FILED wLY 9. l9'07. A 1,221,287. Patented Apr. 3,1917.

V 3 SHEETS-SHEET 3.

UNITED STATES PATENT OFFICE.

WILSON L. CAMPBELL, 0F LA GRANGE, ILLINOIS, ASSIGN 0R, BY MESNE ASSIGNMENTS, TO AUTOMATIC ELECTRIC COMPANY, A CORPORATION 0F ILLINOIS.

AUTOMATIC TELEPHONE TRUNKING-SWITCH AND SYSTEM THEREFOR.

Specification of Letters Patent.

Patented Apr. 3, 1917.

Application mea my e, 1907. serial No. 332,901."

To all whom 'it may concern.'

Be it known that I, VVILsoN L` CAMPBELL,

a citizen of the `United States of America, and resident of La Grange, Cook county, Illinois, have invented accrtain new and useful Improvement in Automatic Telephone Trunking-Switches. and Systems Therefor, of which the following is a specification.

' Myiinvention relates to telephone' systems in general, but vmore particularly to auto matic or semi-automatic telephone exchange systems, and especially to systems in which one or more of the subscribers lines have an individual switch for automatically extendinga trunk connection when the subscriber calls.

Generally stated the object of my invention is the provision of -an improved tele- 4phone exchange system.

Special objects of my invention are the provision of afsubscribers individual trunk lng swltchjhavlng a swlnglng plunger-arm which is capable of opening the bridge norv mally across the calling subscribers line; the provlsron of a brldge-cut-ol' derlceof this character which W'ill'operatelwhen the subscriber calls, but not when the subscriberanswersa. call; the provision of an arrangementby. which battery current for talking purposes is fed to the subscrlbersline through the coils or connections by which the battery is normally bridged'across the said line; the provision of a subscribers individual trunking switch having a trip magnet that is responsive when the sub;

scriber calls, but `which is not responsive when thesubscriber answers a call; and the provision of certain details and" atures of, improvement, and combmatlons ,ndrng ,to

increase the general efficiency hdscrfv-iceability of a telephone exchange `system of this particular character.

To the foregoing and other useful ends, my inventionconsists in matters hereinafter set forth and`clai1ned.

-In the accompanying drawings Figure 1 shows diagrammatically a calling substation A and arcalled substation A connected through the medium of automatic switches (l, I) and To the line #500 of the substation Athere is allotted thesu'itch (l oi an improyed type known as a line switch; and to the line-#22() Lof the substation Af thereis allotted asimilar line 'switch C. At D is represented alirst-selector switch, and

4at E is shown a connector, in connection with which I have elected to explain my in-` vention, they selector beingof the general type describel in 'Patent No. 815,321, granted March 13. 1906, to Keith, Erickson 'and Erickson, and` the connector being an im` proved form of the type `of connector shown inlatent Nc. 815,176, also granted March 13, 1906, to Keith, 'Erickson and Erickson.

The master switch F is provided for .con-- trolling av group of'line switches, of which C is a member. For operating end talkin purposes a Vcentral batteryB having its posltived terminal preferably grounded at G is use Fig. 2 is ar enlarged diagram of the line switch (l and its master switch F. b Flig. 3 is a detail view of the master switch an f.

Figs-4,5, 6` 7, 8, 9 and 10 are detail views showing the construction, and ope ation 4of the impulse-translnittingsprings of scribers telep'ione.

It Will be"understoodl that the lirst-selec-4 tors and connectors may be employed upon the suba percentage basis-that is, in an automatic exchange of one-thousand capaclty a sornel whatcommon arrangement is to' divide the ysubscribers and then allotted, llne swltches into groups oi: one-hundredeach. Theft-t0A each vgroup of line switches `there-is allotted a group of I'irsifselectors, usually ten in num` 1 ber, making, in zione-thousand system, oliehundred first-selectors. To each bank, level .of these Yfrst-selectors there is allotted a group of "connector switches,x usually ten in 'number, which in turn are adaptedtom'ake connection with the subscribers4 lines of that l group. For example, thev group correspondlng to the fils't .level is the one-hundred two-hundred gro1lp,letc.: dl-ed group of subscrlbers of the thousand there is allotted a group of connector approved type. yThose in connection with which l have-elected to explain mypmentioinv cornlntlse. as shown at station A, a'receverQ, Y

a switch-hook 25 for controlling'the substr tion circuits. which controlling-1operrrtiolis en group; the group of the second level is the i thus to each hun-` The substations may be of any suitable or are. aecouiplishid through the '-nediuntl'fl'df any suitable means', such as theoqmarns 4; 4110 -Q i 5 and 6. As the switch-hook is lowered the r:am-arm ,5 momentarily presses the release springs 7, 8 and 9 into engagement, whereby the substation line conductors may be grounded simultaneously. When the switchhook is down the cam-arm 6 maintains a contact between Athe springs'lO and 11, thereby bridging the ringer 12 in series with the condenser 13 across the line. The substation ground circuit'isnormally broken between the ground springs 14 and 15 by the camarm 4g but when said springs are together ground is provided to the ground post 16, and to the release spring 7 as is usually the case i'n'telephonesA of this type. The said substation vcoir1'1'n'i-ses the usual transmitter 17, induction-coil'lS having the primary winding 19 and secondary winding 20. Bein an. automatic substation it is provided with the usual vertical and rotary impulse springs 2l and 2,2. The vertical impulse spring is provided with an oblique projection o r lug 23' (Fig. 4) on the inner side of which the vertical impulse teeth 24 are adapted to engage foidriving the spring 21 intermittently onto the ground post 16. The rotaryv impulse spring 22 is ,proyided with a somewhat siri'iilarmechanism, whereby the rotary vimpulse spring may be driven onto the ground post' once when the dial is ro! tated in onedirection and once when rotated inthe opposite' direction.- Thel said rotary impulse spring 22 has on its inner side a V- shaped member 25 having two sides'c4 and d,

and thereuis in addition an auxiliary spring y26 which' works in conjunetionwith the V shaped memberf shown more clearly in Fig. lathe auxiliary spring 26 is provided with va-.lwer curved part 27 having the rearseetion e 'curving outwardly, as shown in Figs.' 4' I5 and 6. The fr'ont Section 28 of the said member, 27 is designed to fall j ust below the apex4 lof the V-shaped member' 25, so that the'I-otary impulse tooth 29, 'when movedin the direction indicated by the ar-` row in Fig.' l5,` will passi'onto the curved member 27 thuspressingthe rotary impulI spring22onto the rgrourid post 1 6 fora comparatively longtime, as shown in Fig. thus `sending .a comparatively long'impulse to thev line. As Vtheirnpulse Wheel advances,

the vertieal impulse teeth'2et 'approach the lug .23 the yertiea'l impulse spring' 21 Fig.j (3) ,rand eventually thefirst tooth that meets the lug 23 clears. Ithe said lu g, as shown in Fig. 7, but not until after the rotary impulse tootlr 29 clears' or disengages the curved-member 27. As the impulse wheel eontinliesto vadvam'iein the direction indi-v cated by they arrow in VFFig. 7, the succeeding impulse. tooth will clearthe `projection 23, as shown in Fig. 8. Thenwhen the impulse wheel,isreleasedg'rstthe vertical impulse spring 21 is carried into engagement'with the ground post 1G't`w`ice', by theteeth previonsly cleared, indicated in Fig. 9; but as the impulse wheel nears its normal position the rotary impulse tooth 29 passes under the curved member 27 of' the auxiliary spring 26 (Fig.l l0), engaging the V-shaped member 25 directly and for a. short time only, sending the ordinary impulse through the medium of the rotaryl impulse spring to the line;- after which the said member 27 is Cleared (as shown in Fig. f5) as the impulse wheel rem-,lies` its normal position. The operations, as thus described, are repeated ea'eh time that the dial is turned, and lthenumber ofy impulses produced through the medium of the vertical impulse spring is aceuratelyaml 'definitely determined at each operation of the dial. Said .substation is, of course', provided with a dial (not shown) whirh. isseeured to the shaft 3l?, together with the locking dog 3l. l `urtlu-r|nor0. there is :l locking ram 32 that locks the dog 251 while the receiver is on the switch-hooi; to prevent a rotation of the` dial. For operating the impulse springs 2l and 22 the substation is provided with an impulso wheel -l that is. .se cured to the shaft ft), whirh 'impulso wheel carries on its periphery the soaallod vertical vimpulse. teeth 2l and one rot-.lryimpulse tooth. 2S). The said impulse teeth are so arranged that when'tho dial-is drawn down the rotar)1 impulse spring is pressed into con-- tact with 'the fground post,and the impulse springl 21 isnot carried into oontnutvwifth the ground post 1G; but as the dial returns, first the vertifa] `teeth. engage the vertical impulse spring 21, and after they haveeompleted their work the rotary impulse tooth 'line conductor from' passing to theotl'ier.

Means whereby a subscriber may signal. a.

(failed .subscriber (fon'lprises the push-.button l 3H which, when pressed. carries the spring Pif) out of engagement. with the contact pol-nt.;V

4i) and into' engagement 'with the contact 'l i point 4.1, whercl'iy tlu` vertical line eonduetor4 34 is grounded` The line .sw-itch (1;(lf`ig. 2)comprises ail plunger. y-l-2.' plunger-arm.-Jfl, trip niagnet '44 and .switch-release maf'fnet 45')` all foi' Q n h which are built about a suitable base or frame (not shown). The said switch-release magnet is [novidod with' an arnratlue,

46 that is pivoted ona 'p'ir47- which rises from the `base' of the'sw-iteluqfllre salclnrmature carries -pivotally seciirdaonzats -nnd'fa second armature 48 that is controlled by the trip magnet 44. The pin 49 about which the armature 48 moves is carried on the end of the armature 46. The plunger 42 is pivotally secured by the pin 50 to the plungerarm 43, `which latter is in turn pivoted to a'pin 51 that rises fron'4 the Switch frame (not shown). The lug 52 is stamped out of the side of the frame and serves as a stop or rest for the armature 46. Upon the armature 48 issecured the-catchsprin 53 which is adapted to engage the endy 54 o the plunger-arm'43. Furthermore;upon the end of the plunger-arm 43 there'is the arm 55 bearingupon its end theinsulating `bushing 56. This: ar1n'55 .is s o Varranged that when the plu'ngera-rm operates and .thrusts tlieplunger ilntothebanl; the springs'57 and are carried out of engagement with the springs 59 andr GO.n respectively, whereby the `trip magnet 'coils are disconnected from the bat'- tery terminals. The trip magnet 44 comprises two doublefwound coils yG1 and 62 having windings.differentially arranged,

`so tliatwhen one setofwindings of the two coils carry current the tiip magnet 44 opera- -tively energizes; but when both Sets of windings are included `in an energizing circuit the Said magnetfdoes not .operatively yener-v gize. V'Illia general operation of the switch is as follow's .The trip magnet 44 is energized by'a preliminary impulse and the .armature 48 is attracted againSt' ythe magnet cores.

1V hen the arnuiture 48is attra ctedto the left (Fig. -tlie ,catch` slides out of ,contact i with tleend .f4 of lthe.plunger-arm 43,' and the siriiliplunger-ai'm 43, owing to the ten- .sion ofthe springSammies-about the pin 51 andthidu e the plunger 42 intothe bank terminal Q.' Whenthe plunger-arm thus operateathe ami 55v operates the'springs 57 and 58h disconnect the trip magnet from the battery, as explained; andwhen the trip magnet', deinergizea, 4.the vtrip armature 48 `falls againet thejend ofthe plunger-arm '43.

The switch.;srestored Vwhen' the release mag-1' v net45 become? energized, whereby the arI`na ture 4G`iSa'ttracted, and accordingly the tri'plar'rnature 48 is .moved upwarduntil the catch elides lover the end `54; then when the rele:` l, magriet,L45 becomes denergized the 'arm t ure 4( returnsto 'normalposition 4 l* l at rest `against the stop Further ore, sincek tlieplunger-arm 43 in Fig. 2, .against the plunger-shaft and as the saidplunger' Shaft advances 4eachf'tiine v d advanced engagement with thearmature48.V

butre'mai sin; a4 position opposite been successii ely seized, and the plunger.y

shaft again passes to the position it occupied when the plui' ger 42 seized the terminal Q,

the plunger 4i? then returns to normal lockl ing engagement with the said plunger shaft. In the meantime` if the line switch C is again operated, the plunger 42 again engages tlie sam e. terminal.- The said terminal is shown removed from its true position with respect to' the swing of the plunger 42, and the bushing 57 is correel'iondingly illustrated. all Joi the purpose of making the illustration clearer. The terminal Q coinprisee the springs (i8 and (39, 70 and 7l, 72 and 78. and i4 and 75. The said springs are normally disconnected Alroin each other, but are driven into cont act in the abo vc mentioned order when theplunger 42 engages the terminal Q. Normally the plunger 42 is, however, retainml out of engagement with the line switch bank and in either locking or sliding eng; gement with the plunger-controlling shaft "i5, which latter is operated by the master switch F. By sliding engagement I mean that the slot GG of the plunger 42 does not engage the plunger shaft G5, and as the plunger shaft is turned the hub 64 slides upon the sha; but when in locked normal position the s' ot 66, is in engagement with the shaft 6.), and each time the shaft is adtrolling `certain circuits that will be dis closed hereinafter. It connii'ises the following details: A motor magnet 76 for operat- `Vanced the plunger l42 is also advanced.

ing the ratcheil wheel 77, which latter igs designed for operating the plunger shaft 65 through the nedium of the cam 78; also a differential relay 79 for controlling the eli-v ergizing circuit ot the motor magnet 76.

The said master switch also has abank O- comlirieinga 1 lurality ofindividual contact Ys'egnientei and a common metallic segment 80, as shown. in Fig. The wiper 81 is adapted to' remain ui constant engagement lwith the banl-V O.V and to maintain atall times, except when the wiper is passing from the cxtrime lett contact 82 to lthe eX- treme right roitact 83, some one of the segments [(1. 1in electrical.connection, with the common eegmcnti80. As shown in Fig. 3 the lindii'idua'4 Segments a. are separated from the cominon segment by the insulating Strip 84. Thefa'iring 85 is provided in order that when the wiper 8l passes to the lastA contact point $2 then on the next step the wiper is ca rrie lg to the contact 83 on the eX-k treme right, the upper part of the wiper its ` first terminal of the line switch bank,

81 ISlides on the guide. spring' S5, thusl preventing the wiper from plucing any of the individual segments' u .in contact with the connnon segment $0, whcrelrv some interference might he caused with the master switch.. The wiper nl is operated in a stephy--stcp manner hy the ratchet wheel 77 through the medium of the cam member 78 rigidly secured to the said wiper S1 and mlapted to successively' engage the pins 80, S7, SS and Si) upon the said ratchet Wheel 77. The motor nialegnet 7() is provided with an armature il() upon the end of which there is sllitnhl)v secured a pawl 0l. llach time that the :said unxejnet is energized thc pawl 511 engages the ratchet wheel 77, advancing the lutter one riep. ll will he. seen, threetore` t-hnt :le the rzlehel wheel 77 advances the wiper Fil :liso ;ul\';:n -;-r (epl `vr'tep flon'l` `slunee. tlenrsthe run! 7H (he rel Vueling; spring' 02 restores the wiper Si lo il` iii-nt position a1 the right ot' the hunk in eirejzrojmnelit with the lirn segment Si?. 'i`h'. uid motor muguet i 7G is. provided with u couple nl interrupt-er springs 03 :uid-ttl; that ure included in the energizing circuit oi" the said motor magnet, which energizing' circuit alzs'o comprises the shrings 05 and 0G controlled hv the. difieren tia-l relay 79. ',llheretore, \'henever the differential relay is ei'iereizedthesprings 95 and 00 are pressed into contact and the motor magnet 7G operates step-hy-step as longr as the f lifierential relay '70 ren'xains energized. Furthermore. it assume-ll that the terminal Q.v ot the line switch C- is the Vhile .in norn'ial locking' engagement with the shalt 05 the plunger .42 is retninet'l in front of said' terminal by the. plunger shaft 65, whenever the master switch wiper S1 is in engagement with the hunk segment 83:3; but as the. motor magnet '70 advances the Wiper 8l onto the second Segment 07 the said plunger and all idle plungers similarly engaging the shaft 05 are carried opposite the next terminal of the line switch bank. It should be noted that in euch switch bank all of the i springs 68 are permanently connected and may be made of -one common piece; 'the springs 69 are, however, individual-that is, there is one separate and distinct spring -for every bank set Q, there'heing ten `in the bank.` The springs 70, 72, 73 and 74, like the springs 68, are also common, and the.l springs 71 and 75, like the springs 09, are indivi-dual. For. every bank terminal Q, there is :i trunk line of three conductors 98, 99 and 100 leading to a selector; and there is also a normal trunk line comprising the conductors 101, 102 .and 103 leading to the connector banks. The subscribers line conductors Mend 35 terminate, in the. springs (5S and 70.Whic h, as has been stated, are common springs. When the subscriber operates vertical inotion; line relay' 125, and while the side switch 1s 9s;`

the line switch (l and the plunger 42- engages the. terminal Q., the suhscribe1"s line conductors 321 and 35 are extended to the vertical and rotaiytrunk conductors 98 and 99 and thence to the switch D.

The mechanical details o'l the tiret-selector are, in general, 'woll known, involving the .switch shaft (not Shown) which carries the line wipers 104- and 105 and the private wiper 100. The side switch is controlled by the privato magnet 107, and when the switch in normal or first position the side switch wipers 108, 100, 110 and 111 engagethe contact points 112, 113, 111 and115, re-l spectively. In the second position the side switch. wipers engage the contact poi'ntsllt, 11.7, 11S and 110, and. when 'the wipers are in third position the Contact points 120` 121, 122 and 123 are engaged by their respective wipers. After the line switch @has operated and a trunk leading.,r to a first-selectorlnn; been seized. the firstvselector is thcnunler the control of the calling* subscriber through the. medium of the vertical and ro-f .i tary line relays 121V and 125.v lVhile-tho 90 side. Switch is in .the first position the callin-g. lsuhscrilmr controls' the vertical magnetl26v which operates to ,give the switch shaft `a., By means ot'l the rotary in the first or second position, thesubscrliber e i controls the private magnet 107 and, therefore, the side switch.` Then the side switch is in second position the rotary magnet r128 is energized and' th switch Shaft/ that car-` io'p riers the wipers 104, and 106 is ,operated ,in a rotary direction. The Vertical and rotary line relays 124 and 125, acting conjointly, provide the means by which the release magnet 129 is Operated by the siible scriber while the sideswitch is in first or second position4 If the side switch passes to third position, however, since the selecttir D is of the trunk-release type, the release),

magnet 129 isl then controlled througlrthe 11,150

connector E by Way of the private ,\V1}`3e1\ v 106; and by means of the back-releesefrelay 130. f

The mechanical'details of the select-@mandi e connector, as is well 'known,are yery much r11,5 1.

the same. For' instance, the .connector switch shaft '((not shown), 'like the wleetor, carries the line lWipers 131 and-132 and-fr the private wiper A133.A The connector?switch.` 'g

is also controlled-,by the calling',lsiiljscriljier ,120 12,-

through the medium of the verticalv andlfro tary line relays 134. and 135. The vertical.. line relay 134 directly controls the1 .yerticg1 l magnet 136=and also therotary"lnznignet` 137.1;

The function of the vertical magnet, 13.6 isflzefzto give theV shaft andshaft wipers-a verticali;

motion, and the rotary' mngfnet..137` ,imparts I to the shaft and shaft Eviripersm, rotaryor 'circular motion; The rotary: line relay -1;B,5

controls'the private magnet `lif'awhieh I zitilio 1 ond position and a! third position.

(bridge relay p .junction with the vertical line relay 134 to ,suitable design, as, A for y the primaryh winding 154 of yofthe said induction-coil.

` at substation lthe switch-hook and `operates the calling the well-known manner,`

i y 60 Aliininary rotary im i `rotary line, whichiin'pulse, if the selector D ter, under certain conditions, controls in turn the vertical and rotary magnets 136 and 137, the release magnet 1239, and also the side switch wipers 140, 141, 142 and 143. The said side switch, like the side switch of the selector, has@ normalior first position, a secreleasemagnet 139 is also controlled by the vertical and rotary line relays 134 and 135 conjointly. By the vuse of the condensers 144 and 145 the circuit through the connec-4 tor is dividedl into two sections. The connector is provided with a diiferentially wound relay 146 which is composed of the windings 147 and 148. The function oi' this relay 'is to provide the calling subscriber with `talking battery current when the back- 149 energizes, and also in concontrol the ringer relay 15() by means of which the ringer generator His bridged' across the terminals c of the called line to signal the called subscriber.

` The back-bridge relay 149,1 comprising the windings 151 and 152, Earovides the called subscriber with talking ttery current when' the primary circuit of `the called substation is bridged across the line; .The central station is equipped with the busy signaling apparatus I, of any example, the one comprising an interrupter 153 `in series with c the induction ycoili155, whereby a busy signaling current is induced in the'secondary` winding 156 When the connector shaft is raised one or more steps the Secondary winding 156 is connected with the `sdefswitch Wiper 141 through the normal springsl' and 158 when ,the side switch is in first position. l l `The o erationof my improved line switch C `may e ynore clearly understood from a descriptio of ay call, as follows: To call the number 2..,0 (substation iA) thesubscriber A removes his receiver from device once, 'in

for each digit. lVhen the dial is rotated i for the first digit a preliminary impulse is transmittedy overthe rotary line conductor.

This preliminary impulse energizes the trip magnet 44wheieb the line switch C is opl erated toseize an `idle trunk line,y leading to a first-selector. In returning to normal position orthe first digit the dial operates the lirstiselector switch to establish connection i `Withvan idle trunk line leading to a connector. Of course, it will be understood that when the dialis turned foreach digita preulse is transmitted `to the or a connector E isy on th line, is receivedV f c ybythe rotary line relay of the switch while the side switchsin first position. -This rotary line relay, of course,y energizes; but

, pulses.

rotary line relay causes the private magnet The since the side swi 3ch is in first position this is without effect, :ind the switch is not operated until the dial delivers the vertical im- 'l`his preliminary operation of the to be energized and deenergized once,` but inthe switches disclosed 1n the said selector `and connector pr tents the sideswitch can under no circumstances leave the first position until after tle'vertical magnethas beeinf i operated one or more times. Said-preliminary impulse is effective only in operating the line switches. The impulses for the last tw'o digits are'dii eeted toward the connector E which operates to place its shaft wipers in connection with alie contacts corresponding to the desired lim. The preliminary impulse for operating the line switch @that occurs when the calling subscriber rotates the dial forward for the first digit is caused by thev rotary impulse spring' 22 being pressed against-,the grouiid post 16. i As a result of the impulse the trip magnet 44^of the line yswitch (lis lenergized by a flow 'of current `from ground G to the springs 14 and 15,

ground postI 16, impulse spring 22to the rotary line conductor 35, conductor' 159 (Fig. 2), through thelwindings 160 and 161 of the trip magnet coils 62 and 61, cut-ofi' springs 57 and 59 to the battery lead 162,)thence .r

through battery" B to ground G. `rls soon as the trip vmagnet 44 energizes, the armature 48 is attracted, and the plunger 42`is liberated and thrust into the bank terminal' Q (assuming that the plunger 42 is opposite this particular terminal at the time) by the spring 63. The plunger, upon thus operating, moves the p liinger-arm 43 about the `pin v51, whereby the arni55 uponvthe end ofv the plunger-arm cai ries the springs 57 and 58` out of engagement with the springs 59 and 60. The disengagement of the'springs 57 and liireaks the energizing circuitthrougli tli'etrip magne"l 44; tlile said Vtrip magnet then `de'eliiergizez; and permits its armaturey 48 to fall back--that is, the spring catch 53 falls against the terminal piece 54,as shown, When the plunger 42 engages the bank terminal Q an yenergizing circuit is. closed through the mot or magnet relayi79, which in lturn operates to close an energizing circuit through the meter magnet 76." The motor magnet then operates to advance all idle plungeis in loi-.king engagement with the shaft 65 to a poi ntopposite the next idle bank 120 terminal, simila r to the terminal Q.V lThe circuit through lher relay 79y extends from ground Gr2 through the winding 163 of the `relay 79, segment y80, wiper arm S1, segment 83, conductor 164, bank terminal springs 7 5 and 74, release magnet 45 to the battery lead 162, thence through battery B to' ground G. Although thiscircuit `includes the release magnet 45;, the magnet 45 does not o eratively energize` since the windings o thema relay 79 are of a high resistance, while the winding of the release magnet 1s comparatively low. The relay 79'* upon energizing operates to place the springs 95 and 96 in ing circuit through the motor magnet. The

cam 78 being in engagement with Vthe pin 86 is operated to advance the plunger shaft and all idle plungers that may 'be in normal locked position with the shaft 65 one' step opposite another trunk terminal, similar to the terminal Q, assuming the next succeeding trunk is idle. Consequently, the wiper 81 is carried from thev contact point 83, which corresponds to the terminal Q, to the vcontact point 97, which latter corresponds to the terminal bet'ore which the advanced idle plungers are now resting. Suppose that nine subscribers havecalled and that the mast-er switch has Abeen thus operated nine steps,k carrying the wiper 81 to the last contact point 82. Now, when the motor magnet 76 operates for the next step, when the tenth subscriber calls, the wiper 81 passes back and drops into engagement with the contact point 83, as already explained. lt' the trunk is still busy the wiper Silinds. battery cur rent on contact 83, and an energizing circuit `is established through the ditlerentlal relay 79, which in turn operates to close an energizing circuit through the motor magnet 76. The current through the said relay 79 l'lows from the said contact 83 through -the wiper 81 to the common segment 80, through the winding 163 of the diliferenl'ial relay 79 to ground (il. lVhen the dllr'erentlal relay 79 attracts its armature the. diti'erential relay springs 95 and 96 are pressed into contact, therelrv closing an energizing circuit .tor the motor magnet from ground (iJ through the said springs 95 and 96, through the motor magnet springs 93 and 9+, motor magnet 76. thence A.to the battery lead 162 and through batteriv l vto `ground (i. The molor magnetthen operates, as previously explained, to rotate the ratchet wheel 77 one step for advancing the plunger shaft 65 one step and the master switch bank wiper S1 one step also andinto engagement with the 'second segment 97. The plunger shaft 65,

' when thus advanced. one step, carries all idle plungers that are in locked engagement with the saidshaft to a point opposite the next bankiterminal, as previously explained.

It' there should still be a guarding potential at the bank segment 97 of the master switch bank, the differential relay 7.9 will, remain energized.. whereby the energizing circuit through themotor magnet 76 is again' completed whenthe motor' magnet springs 93 and 9s againv engage; anda's a result the motor magnet 76 is again operated, `whereby Ythe plunger shaft 65 and the master switch wiper 81 are advanced another step. vThis operation continues as 'long as the wiper 81 continues to'lind segmpnts with guarding potentials. As soon asan idle segment is found, however, the energizing circuit through the ditferentialrelay 79 .is broken, at which time the said relay in turn breaks the energizing circuit for the motor magnet 7 6 until the next subscriber makes a call. At the instant'that the plunger 42 enters `the said bank terminal Q the following springs are pressed into contact: 68 and 69, 70 and .71, 72- and 73, and 74 and75. The engagement of the springs 72 and 7 3 establishes a, guarding potential, by way of the normal l conductor 1,03, at the connector private bank contacts corresponding to the linllJ that terminates in the line switch C, to prevent any subscriber from callingthe said line after the calling subscriber at substation A operateshis dial preparatory to making a call, as explained. The circuit over which the said guarding potential is established extends from ground Gr4L through the bank springs T2 and 7 3 to the private normal conductor 103. Also, the closure of connection between the springs 74 and 7 5 establishes a guarding potential at the master switch bank contact 83 over the following circuit: from battery Bfto the battery lead/,162,

thence `through the release magnet 45 and springs 74 and 75 over the conductor 164 to the said contact point 83. It will-be understood that the bank terminalI Q, being the i first bank terminal of the line switch bank, .corresponds to the first segment 83 of the master switch bank O and, therefore, to the trunk line conductors 98, 99 and 100 which terminate in the selector D. This guarding potential protects the seized trunk conductors 98, 99 an'd 100v from being seized by other plungers, as already eXplained.

-The closure of. connection between the ,springs 68 andl 69 extends the calling subscribers vertical line conductor 34 tothe vertical trunk. conductor 98 and to the side switch wiper 108 of the first-selector D. The closure of contact-between the springs 70 and 71 in a similar manner extends the subscribers rotary line conductor 35 to the rotary trunk conductor 99 and to the sideswitch swiper 109 of the selector D. The subscriber has thus established connection with the selector D which `is nowy operated by the impulses that are delivered as thel dial returns 'to normal position. The first,

Iso

digit being 2 the spring 21 is pressed onto the ground post 16 twice. As a result the vertical line relay 124 of the first-selector D is energized each time by a flow of current |5 from the substation ground G through the springs 14 and 15 to the ground post 1 6, thence through the spring 21 to the vertical line conductor 34,' line switch bank springs 68` and 69, vertical trunk conductor 98, side switch wiper 108 of the selector D, contact point 112, vertical line relay 124 to the battery lead 162, thence through battery B to ground (lr. lllach time that the vertical. line relay 12:1 encrgizes, the line relay spring 15 166. is pressed onto the ground spring 165. The vertical magnet 126 is thereby energized. and the wipers 104, 105 and 106 ot l the selector D are raised to the second bank ,level opposite the iirsl contact'of said level. `T he energizing circuit tor the said vertical magnet 126 extends from ground G5 through the springs 165 and 1667 private springs 167 and 168 to the vertical magnet 126, thence to the l-alttery lead 162 and tlnfough battery B to ground (lr. Following the rertical impulses the rotary impulse spring 22 is then pressed onto the ground post 16, grounding the rotary line conductor and energizing, there-taufe` the rotary line relay 125 of the selector D. The energizing current passes from ground Gr to the rotary line conductor thence it Hows throughthe line switch bank. springs 70 and 71, rotary trunk conductor 99, side switch wiper 109 of the se- 435 lector D, contact point113 to the rotary' lineA 4relay 125, to the battery lead 162 and through battery B to ground G. The rotary line relay upon operating presses the line relay spring 169 onto the ground spring 165, thereby establishing a circuit through the private magnet 107 from ground G5 through the syn-ings 165 and 169 to the @private magnet 107, thence through the said magnet to the battery lead 162, and through battery Bf to ground Gr. The private magnet, upon energizing and deenergizing, permits the selector side switch to pass from `first to second position, permitting the side switch Wipers 110 and 111 to engage the contact points 11.8 and 119, respectively. Th e closure ofconnection between the side switch wiper 110 and the contact point 118 l sets up an energizing circuit for the rotary magnet 1,28 from ground G to the contact point 118, through the side switch wiper 110, interrupter springs 170, rotary magnet 128fto the battery lead 162,1and through battery B to ground G. The said rotary `magnet V128, then operates to rotate the wipers 104:, 105 and 106 bf the selector D into en* ga ement .with the first contact of the seeond level lof, the selector D, 'from which contact, it is assumed, the trunk line conductors 171,172 and` 173 leadto the connector E. Iithe first trunk. is busy, however, and the tery lead 162, and through batter wipers pass over -busy trunk lines, then as soon as the private wiper 106 engages the first grounded private. bank contact point, the private magnet 1,07 energizes again, looking the side switch in second position. 7g The energizing c .rc-uit for said prlvate magnet extends frorrv the grounded terminal' Gr 4o1" battery B through the occupying switch (not shown) to the private wi er 106, thence over the conductor 174 an through the 75 back-release relay 130 to the side switch wiper 111, contatt point 119, private ma net 1.07, thence throrgh said magnet to the at- `B to ground G. The private magnet 10 upon go thus becoming energized, locks the side switch wiper 11) in en agement Awith the contact point 118,v where y'the rotary ma net 128 will be energized intermittenti;r until the wipers are carriedbeyond the last 35 busy trunk line. Atthe instant that the private wiper leaves the last busy contact point the, energizing circuit through the private magnet 107 is destroyed, and as a result the selecx'rr side switch asses to 90 third position. If, however, vt ere are no busy trunk lines, the rivate magnet 107 releases yche side switcli to third position as soon as the Wipers are carried' into engagement with the first trunk line. As soon as th'e side switch passes to third position, as stated, the subscribers line conductors 34 and 35ers extended to the conductors171 and 1723 which, in this case, it is assumed lead to tie connector switch E. The extension of Vthe` line occurs, of courseras soon` as the side switch wipers 108 and `109 engage the cont 1ct points 120111111121, resi'eectivelyy Not only is thesubscribers line tnus extended, but a'guardingpotential is-105 established at the private wiper 106, when the side switch wiper v 11j-*passes onto the ground contact point 123, for protecting the l seized trunk lint from' interference by other calling subscribers. llhis guarding ,poten-11o tial is established from ground G7 to the contact point 15:3, thence through the side switch Wiper 111, thro'ugh the back-release relay 130, conductor 174 tothe'private wiper. 106. Itwill be evident, of course, thatthe energizing circuit for the rotary magnet 128, Y to which reference has already been made, is destroyedfwhen the idle trunk Aline is seizedthat is, when the side switch Wiper llleaves I l the `Contact poi-1t 118; The grounding-i ot'12e I .the line conductors 34 and 35i-"for the last two digits affects 4the connector by operating, the 'vertical and lrotary line relays 134 and 135. When the said vertical line conductor 34 is grounded the vertical line relay 1341s 125% energized by a ow of current' from the sub, station ground` G', verticallimpulse spriner 2lrto the vertical line conductor 34, ban

springs 68 and 39, trunk'conductor98, side switch wiper 1.08, shaft wiper 104, condite-'130 Y effect.

-a vertical direction o-ne step at a time until and' the said Wipers areY carried two steps thus broughtopposite a level. in which are located the terminals of the line #220. 'I he circuit through the vertical magnet 136 extends from ground through the springs 176 and 177, Vprivate magnet springs 178 and v179, side switch wiper 14.2, vertical magnet 136 to the battery lead 162, and through battery B to ground When the rotary line conductor is grounded, following thc vgrounding of the vertical line conductor, the connector rotary lineI relay 135 becomes energized through a circuit extending from the substation ground through the rotary impulse spring ,22, rotary line conductor bank springs and 71,.conductor 99, side switch-wiper 109, shaft wiper 105, conductor 172, ,rotary line relay 135, winding 1.48 of the differential relay 146, through the springs 18() and 181 to the battery lead 162, thence thro-ugh battery B to ground Gr. he winding 14S of .the dil'l'ereiitial relay 1,16 being included in thisv circuit, as is also the winding 147 'in the vertical line relay circuit, the .said relay 1&6 energizes, lint with no effect. rl.`he.rotary line relay 135, upon energizing', operates to close an energizing' circuit through the private magnet 1215, which latter l tui-n operates to releasethe side switch from iirst to sei-ondA position.

EThe energizing circuit through the private n'iagnet 13S extends from grouinl(ilH-thi'ough the springs 176 and 152, through the p rivatc nia-guet 138, springs 1S() and .1.51v to the bat- I" tory lead 162-', and through battery B to ground G. For the last digit the subscriber operates the dial as pi'oviolisly` described, grounding the vertical line conductor 34 ten -ftiinesand the rotary line. conductor ai once.

The connectorvcrtical and rotary line relays 134- and.135are operated over previously traced circuits. lllowevcr, when the vertical line relay opel-ales, a. circuit is closed through Vthe rotary magnet 167 instead of through the'vertical .inagnet 136, since the side, switch Wiper Mit-is now .in second post tion. Each time that tlieiotai'y magnet is energized thesha'lt iriifiers 131, .1i-32 and 133 are i'ci-tateilone step at a time until the said, Wipersv are carried into engagement With the normal conductors 183, 184 and 1155, the vfirst two of whiilrconduetors leadi to the line terminals of'the vdesired substation.

The Wind-` that the former result occurs, and that the side switch passes to third position, Whereby the side switch wipers 1l() and 141 are placed in connection with the shaft lwipers 131. and 132, respectively. Furthermore, when the side switch passes to third position a. guarding potential. is established for protectilig'tlie called line. This potential extends from ground (.i" through the ,side switch wiper l-lI-, conductor 186 to thc private wiper .l-5:5, which latter engages the private'rontart of the called line. .ln Order to' signal. the suhsrrilar at substation A presses the Isignaliii --huilon 3S, whereby the i'ertical liiul i-oiidiu-l'or -l is grounded, and the roniiertoi vertical line relay 131 and thel ditl'ereiitial relay lll-(fi heroine ei'iei'gized as lseloi'e. ll' will lie renieinlieied that the side switch has passed vfrom sei-ond to third position.l and that the .aide switch wiper 142 is in engagement with the contact point 1F37, thereby placing the vertical line relay 131 in coiitrol'ot the ringer relay 150 in the saine manner in which the rotary inagnet 137 came under the control ot' the vertical -l iiie relay when/thc side switch missed from lirst io second position. rtherefore, when the. vertical line relay presses thc 'springs 176 and 177 into contact the ringer relay 150 energized by` a flow ot' current from aggifouiidfGs Vthrough the .springs 176 and 177, private magnet springs 178 and 179, sido switch wiper 112, contact point 187, ringer relay 160, springs 13B and 180 (bearing in niind that the. diflereiitial relay 1'16 is energizedl io the battery lead 1 62,theiice through battery l to lground (i. r1`lie ringer relay, upon energizing', shifts the, spring 1.9() from i contact with tliespi'iiig '191i into engageii'ieiit with the spring 192, and the spring 193 is shifted into ei'igageinent with the sprii'ig 191. rl`h1s resultel in bridging across the called suliscriheifs line -theterininals of the.

switch wiper 1411,4 ringer relay Springs 190 Y and V192 back to the generator 'H. As soon as the calling subscriber ceases to press the signaling button 38 the ringer relay 150 be. comes denergized and the springs 190 and 193 assume their normal position. The sub.

los

scriber at substation #220, in response to the signal, removes tlie receiver 203 from fthe switclnlioolr 204:, whereby the switchhook ris and peri'i'iits the springs 205 and 206 to en fz and the springs 199 and 200 1 t "to disei'igagc, therel'iy removing the ringer 108 from across his line, The engagement of the springs 205 and 20o closes a series energizing circuit through both windings of the relay 140 at the ifoi'iiiectoi F, this circuit extending from ground G to the side switch wiper 143, winding 151. oi" the relay 110, side switch wiper 140, (,fontact point 105,

)shaft wiper 131, vertical. normal conductor .called sul'istatirin, trans 1S3, vertical line, conductor 100, springs 205 Iand 200, th rough the maling device of the 'tter 207, primary `winding .208, vertical line conductor 201,

.l'iatteiy current through the trip magnet 213 of the line switch C,

as Jr'ollows from ground (iwtlirough the'springs 214; and 215, through the windings 210 and 217 to the i `ing supplied with current in this manner,

i does not imerativell vertical line normal uconductor 183, thence through the sul'istation transmitter 207 to the rotary normal ('.iiinductor 184, as pre `.viously traceil,` then tlirougli the windings 218aand 219, springs 220 and 221 to the battery lead 162, thence through battery B to ground (lr. The trip magnet 213, upon bel energize,l since the windings 216 and 21 are so arranged that they neiiti'alize 'theenergizing effect produced by the Windings218 and 219. The` relay 149, upon ciiergization, operates to shift the spring 180 from the spring 1.01

(which latter is connected to the battery lead 102) to the spring 210, which is in tur1i connected with ground. The reversal of the polarity of the spring 1.80 sets up a circuit which provides the calling subfstation with `batterycurrent for talking purposes. This `circuit may be traced from 'ground G -to the side switch wiper 11113, through the springs 210 and 180, windingll of` the dii `fereii'i'tinl relay 140, rotary line relay 135,

coni'lni'ftoi- 172, shaft wiper 105, .side switch 10i), coiuluctor 00, springs 71 and70, rotary line coni'luctoi" 35, primary winijling 10, transmitter 17, i )rings :"t' ani B7, vertical Alinie i'ioniluctoi' 34a, bank 0S and ill),

conductor 98, side switch wiper 10S-'4, shaft wiper 10.1-, ci'ii'iductor 171, `vertical line relay 134, wiiiiling 147 of the ditierci'itial relay 146 to the battery lead 102. tlieni'ne tl'irougli battery B to ground (l. Both p'iiidings of tl1 'e. i'elay 146 now rai-ry cui-riait, but the windings are so arranged that the said relay imm not. .operativel y energize. The vertical `ing ,14:8 aids the wi iding` 147 in` maintain and rotary line relays 134 and 1.35, being included in the above circuit, operatively en- P' I ergize and, place the springs llo, 177 and 182 in Contact, and the release springs 211 and 212 vare also brought into contact; but the simultaneous action of these relays at vthis particular time is without effect, since `ooi'itact of the said release springs grounds `the vertical and rotary.` line conductors 34 85 and simultaneously from ground G to the release spring 7 thence 4througggh the springs S and fl to the rotary 'and vertical line coiidnctors. The grounding of the ro# v tary line Acilinductor 35 produces a short 90..

circuitof the rotary ine relay 135 in series with the `winding 14E of the differential relay 14, said circuit extending from ground f* il" at thecoiinectorto the side switch wiper 143, springs 210 and 180, winding 148 of 95 the diierential relay 146, rotary line relay 135 to the shaft Wipei 105, side switch wiper.y 109, trunk conductor 09banlc springs 71 andk vto therotary line conductor 35, release springs 8 and 7 to, the substation ground'ioo G. Therefore, sine: the Winding 147 of the (liiferential.relay 140 alonecarries cui'- rent, the said relay recoines energized and` attracts its armature, which shifts ythe :f spring 189 out of contact with the spring 105 20S.) and into contact Vwith the spring 188. The disengagement of the springs 209 and ,i 189 destroys the energizing circuit through the relay 14:0, and th e spring 180 passes out of engagement with the spring 210 and into 11i,` engagement with the spring 181, which re* moves the said shor t-circuit of the rotary line relay and u inding 148, and estab lisbes an energizing circuit instead extendi ing from the substation ground G through 11!!` -the release springs and S to the rotary vthence through liiatteiry B to ground G.

The rotary relay '1515i now operates-and the springs 211 an 212 come :into .ci'intach whereby :in eneigiz/ig circuitis estal'ilislied through the release iiiagnet 12110 o1 the cou-` 12B hector E and the rlcase 1 lay 130 ot the selector l). t-lowerer, .the current nrgiiw in passing, as above strted,through-tl1eyviiid-` .iugll'ie springs 180 i nd 195i in rfuitact "The v battery B to `the switch shaft and energizing circuit through the release relay 130 and release magnet 139 extends from ground G7 at the selector' D, side switch wiper v111, release relay 130, shaft wiper 10G, conductor 173, trunk-release springs 211 and 212, release magnet 139, springs 188 and 189 to the battery' lead 162, and through ground G. Vlien the connector release magnet 139 is thus supplied with current it enero'izes, and as' aresult Y side switch are restored to normal position, thus breaking the connection between the connector switch shaft wi ers 131, 132 and 133 and the normal con uctors 183, 184 and 185. The backrelease relay 130 being in the same circuit with the release magnet energizes simulta-n neously with the latter, and operates to close a circuit through the 'selector release magiiet 12,9 by pressing togethei' the back-release springs 222 and 223. Also, when the springs 222 and 223 engage, an energizing circuit is closed through the release magnet 45 of the line switch C extending from ground through the springs 222 and 223, bank springs 75 and 74, release magnet 45 to the battery lead 1,62, thence through battery B to ground G. The circuit thioughthe said release magnet 129. extends from ground through the release springs 222 and 223, through the release magnet 129, thenceto the battery lead 162, and through battery B to ground G. When the ground to the line conductors 34 and 35 is interrupted' alltlie magnets involved in the release 'are 'denergized and all of the switches arey fully restored. If the called line #220 is busy4 at the time that the calling subscriber #500 attempts to establish connection, the connector E is released by the last impulse to the rotary line conductor 35, as follows: The said impulse energizes the rotary line relay 135 of the connector E, which relay in turn energizes the private magnet 138,

pressing the private springs 224 and 225' y into contact after the private wiper 133 has been carried onto the grounded'private bank contact. whenever .the line #220 is busy the connector private bank contacts connected with the privatenormal `185 are` all connected t0 ground. Therefore, since the connector .side

switch is in second--Y-positioii when the pri- .ateii'ia'g'net springs 224 and 225 are brought into contact, an energizing circuit is established through the release magnet139 from the said grounded private bank contact to the private wiper 133, thence to the side switch wiper 143 (which is iii second position) to the private magnet springs 224 and 225, to the release magnet 139. through the springs.`188 and 189'to the lbattery lead 162, thepce through battery B to ground G. The connector switch shaft and side Of course, it is understood that switch are thus released, and "connection is not Vestablished with the called line. Now, when the calling subscriber presses the signaling button, the vertical line relay 134 Abecomes energized and operates to close a connector E, as already explained, producing the release of the switching apparatus as formerly.

From the foregoing it will be' seenthat I provide a common battery system in which current for talking purposes is fed to a subscribers line through the coils by which the battery is normally bridged across such line. For example, as shown in Fig. 1, the called subscribers line is normally connected with the opposite poles of the battery B- through the-medium of the windings 216, 217, 218

and 219, and when this line is called this connection is retained for feeding the t'alking current to the line. In this way, as stated, means are provided for automatically trunking callin -lines into connection with called lines, an at the same time pro-- vision is vmade for feeding talking current to a subscribers line through the medium of the normal' connection between that line and the common battery. It will be understood, of course, as previously eiiplained,

that the talking current also flows through the coils of the back-bridge relay, and is fed through these coils to the called line, so

that the back-bridge relay windings are in multiple with the trip magnet windings of the called subscribers line.l In this-way it lis .not necessary vto open the bridge normally existing across the called subscribers line, because closing the called line does not energize the trip magnet of the individual switch C, inasmuch as this magnet is differentially wound. of the calling subscribers line is, however, equipped with means for opening the bridge across the calling subscribers line, in the manner explained. In other words, the energizingof this trip magnet causes it to open its own circuit, thus keeping the bridge open as. long.' as the plunger-arfin43 is in position to maintain the connection between the calling subscribers line and the trunk line. Furthermore, the differential windings of the trip magnets make them unresponsive to ringing current, when ringingcurrents are sent over the called lines to signal the calledsubscribers. It will-be seen that the called subscribei"s trip magnet does not The plunger-arm 43 said individual switch comprising electromagnet windings bridged across the said line responsive only when said line is calling, and the connector being provided' with electromagnet windings adapted to be connected in n'mltipleI with the said windings of the individual switch, and a common battery for feeding talking current through all of said windings to the said line.

14. In a telephone system, a suitable-line, 4

means for seizing the line, means for preventing seizure of said line vwhen the same is busy or already in use, anindividual is 1- numerical switch for said line having a releasable plunger-arm and a differentiallywound trip magnet, and trunks adapted to be selected by said switch.

15. In a telephone system, a suitable line, means for seizing the line, means for preventing seizure or' said line when the same is busy or already in use, an individual switch for said line having a releasable plunger-arm and a di[ferentially-wound trip magnet, and trunks adapted to bc selecte-d by said switch, said magnet having windings connected with the line. adapted to neutralize each other when connected. in

series, whereby said magnet is unresponsive.

to battery current flowing in both sides of the line in series, or to ringing currentV projected over the line. i

16. In a telephonesys'tem, a suitable line, means for seizing the line, means for preventing seizure of vsaid line when the same is busy or already in use, an individual nounumerical trunking switch for said line, and trunks adapted to be selected by said switch, said switch providedwith a differentially-wound magnet connected in the initiating the operation of said switch to seize the preselected trunk.

18. In a .telephone system, a suitable line, means for seizing the line, means for preventing seizure of said line when the same is busy' or already in use, an individual trunking switch Jfor said line, trunks to be selected` by said switch. the said switch comprising a. releasablc p|ungcr-arm, a tripvn lagnct normally bridged across the line, and means operated by said plunger-arm for opening the said bridge across the line.

l19. In a telephone system, a. suitable line, means for seizing the line, means forrprcventing seizure of said line when the same is busy or already in use, an individual trunk- 7 ing switch for said line, trunks to be selected by said switch, the said switch cornprising a releasable -plunger-arm, a trip vmagnet normally `bridged. across the line,

means operated by sald plunger-arm for opening the said bridge across the line when l venting seizure of said line when the same is busy or already in use, an individual trunking switch for said line, trunks adaptedv to be seized by said switch, a magnet bridged across the line and adapted to inl tiate the operation of said switch when the subscriber calls, and provisions for making the said magnet unresponsive without opening the bridge when the subscriber answers;

21. In a-telephone system, aV suitable line` means for preventing seizure of said line when the same is busy or already in use` an individual trunking switch for said line, trunks adapted to be seized by said switch,

and a. connector for seizing said line, said. individual sw1tch comprising electromagnet' wlndings bridged across the said lme, re`

sponsive only when the line is calling, and the connector being provided with electromagnet windings adapted to be connected in multiple with the said windings of the individual switch. y

22. In a telephone system, a suitable line, means for, preventing seizure of said'line when 'the same is busy or already in use,

VVan individual trunking switch for said line,

trunks adapted to be seized by said switch,

- a connector for seizing'said line,'said individuall switch comprising electromagnet windings bridged across the said line responsive only when said line is calling, and the connector being provided with electr0- magnetv windings adapted to be connected in 'multiple with the said windings of the individual switch, and a common battery for feeding talkin current through all of said windings to t e said line.

23. In a telephone system, a subscribers line, an individual non-numerical switch therefor vhaving ka rele'zlisable plunger-arm and a differentially-wound trip magnet, and trunks adapted to be selected by said switch, said system being operative by vertical motion of certain elements thereof to select groups and b rotary motion of the same elements to t en connect -with the called lines found in the groups selected by the vertical motion. l

24. In a telephone system, a subscribers line, an individual non-numerical switch therefor having a releasable plunger-arm and a differentially-wound trip magnet, and

trunks adapted to be selected by said switch, B11-id magnet having windings connected with the line, `adopted to neutralize each other when connected in series, whereby seid nlugnet is unresliionsive to battery current {lowng in both sides of the line in'series, or to inging current projected over the line, seid system being operativeby vertical motion bf certain elements thereof to select groups and by rotary motion of' the snmeelements to then connect with the called lines found in the groups selected by the vertical motion, im In n tele ibone system, o iesubscribel."s y linru un indivi unl non--niuuericul trunking switch for seid line.:1nd trunks adapted to be seized liiy'said switch, said switch pro vided with. e differentially-Wound. magnet colruiectruilw in the linefnnd ,provided with ineens for initiuting the operation of said' witch yto seite an idl t;rt1nk`P seid system being; operative by vertical motion of ceri tuin, elements 'thereof to` select groups and y wby rotary motion of the seme elements to itlien connect with the celled lines .found in the groups selected by the vertical motion. 11; 26, In e telephone system, a subscribers `line, un individuel. non-numerical trunking switch for seid liner trunks ade ted to be e L yreim-ed by seid switch, ineens for se eating the do' trunks ahead of the calls, and a diereir i '.lywvound rnugnit connected in tbe said line andv provided with menus for initiating 'tlie operation of Suid switch to the pre selected trunk, said systenii beingr operative by vertical motion of certain elements there-` of to select groups and by rotary motion of H the sume elernentsto then connect with the `rulled lines found in the groups selected by i u tbe `vertifuil. motion Y w le hone system, a subseribers line, an indivi nel non-ruimerioal trunking switchfor said lineytrunks to be selected by `id switch,l the seid switch. comprising :t renoble plungenarui, u trip magnet non ly bridged across the line, and menus opy by Suid plunger-ernia `for openingu the bridge ii,c1osstheline,suid unbcingg ,ive by vertical motion of t ,rtuin ele- `thereof to select groups und by rotary otion of the suine elrments to then connect e called lines fonnd in the groups j the verticalmotion,

uA telephoner systcn'l', u' i subscriber-s 'n individual non-numerical truiilriug r said line, trilnks to be selected by yh, the said switch eol'nprising le. yiilunger-urrn, o 'trip magnet norun f m e across the line when the si und means rfor prove villswitch when the y' rn being operutivr l tion of l, rtuin elcl'nent-s ti of to select; {grou} und by rotary motion of the bridged Aacross tlurlinc, ineens operby sind plungeiferxn for openi` t e sume elements tu then connect with the called lines 'found in tie-groups selected by the vertical motion., i f

29. In ai telephone system, line, un `individluil nonniumerical trunking switch for Sait. line, trunks seized by vsaid switch, n magnet bridged across the line und adopted to `initintethe operation of sai d switch `when the subscriber cells, and provisions for `making the said l magnet unresponsive Without openin y, the

bridge when. the subscriberunswers, sal system being operative by vertical motionho certain elements reof to-selecty oupsand by rotary :not on of the same e ements to tben'connect u ith the calledvlines found in tbegroups selezted by the vertical motion.

rcelled lines found in the groups selected by the vertical motion y ,i l

3L In u teloihone system, e snbscribers line, an individuel non-numerical trunkin switch therefor, trunks adapted to-be seized bylsuid switch 'n connector for seizingsaid line, seid indii idual switch comprising elecl tromegnet wir dings bridged across the said line res insive only when said line is culling, and the connector being provided with electroinognet win dings adapted to be connected in multiple with the said windings 'of the imlividunl sw tch; and e common battery for feeding talking current through all of seid windings to the said line, said system being operative by vertical motion of certain elements there of to 'select groups und by ro tury motion ofthe some elements to then. connect with theculled lines foundin the! groups selecte d by the `verticaly motion.y y 32. In u. telephone system, u slutnblefline,l

means for pr eventing `seizure ofV said line when the same is busy or ulrend in useyan individuel nt n-nrrnnerical switc `for smid line hurvinl e relezrsuble plunger-arm and u dillerentiu ly- Wouml trip magnet, and trunks tedv y seid switch, said 'eby vertical'.i'notion of adopted to be sel s stein being opemt certeinfelemer ts tliereo'frtd select groups and by rotury motion of the saine elements to1 then connect with tb 'felled lines found in;

,lect tl e vertical motion.

so. 1n. u ttf er n u em, a suitable linee ineens for preventing serrure of seid line adapted to be i In atelffnhone system,` a. subscribers line, a,n1nd1v1| 1 a subscribers y when the same is busy or already in use, an individual non-numerical switch for said line having a releasable plunger-arm and a diierentially-wound trip magnet, and trunks adapted to be selected by said switch, said magnet having windings connected with the line, adapted to neutralize each other when connected'in series, whereby said magnet is unresponsive to battery currentd fiowing in both sides of the line in series, or to ringing current projected over the line, said system being operative by vertical motion of certain elements thereof to select groups and lg rotary motionof the same elements to then connect with the `called lines found in theY groups selected by the vertical motion.

34. In a telephone system, a suitable line, means for ypreventing seizure of said line when the same is busy or already in use, an individual non-numerical trunking switch for said line, and trunks adapted to be selected by said switch, said switch provided with a differentially-wound magnet connected in the line and provided with means for initiating the operation of vsaid switch to seize an idle trunk,.said system being operative by vertical motion of certain elements thereof to select groups and by rotary moy tion, of the same elements to then connect.

switch, the said -switch comprising a releasable plunger-arm, a trip magnet normally with the called lines foundin thel groups selected by the vertical motion. v

35.\ In a telephone system, a suitable line,

means for preventing seizure of said line whenthe same is busy or already 1n use,

an individual non-numerical trunking switch for said line, trunks adapted to be seized by said switch, means for selecting the trunks ahead of the calls, and a differentially-wound magnet connected in the said line and provided with means for initiating the operation of said switch to .seize the preselected trunk, said system being operative by vertical motion 'of certain elements thereof to select groups and by rotary motion of the same elements to then connect with the called .lines found in the groups.

selected by the vertical Inotion.V '4 36. In a telephone system, a suitable line, means for preventing seizure of said line when the same is busy or already in use, an individual non-numerical trunkin switch for said line, trunks to be selecte by` said bridged across the line, and means operated 'by said plunger-arm for vopening the said bridge across the line, said system being operative by vertical motion of certain elements thereof to select lrouprs and by rotary motion ofthe same eements to then connect with 'the called z-zlines, found in the groups selected byfthe vertical motion. 1.

37. In a. .telephoneV system, a suitable line, means for Y preventing seizure of ,saidhline when the same is busy or already in use, an

individual mon-numerical trunking switch for said line, trunks to be selected by said switch, lthe said switch comprising a releasableA plunger-arm, a trip magnet normally r bridged across the line, means operated by said plunger-arm for opening the 'said' bridge across the line when the subscriber calls, and means for preventing actuation of` said switch when the subscriber answers, said system being operative by vertical motion of certain elements thereof to select groups and by rotary motion of the same n elements to then connect with the called lines found in the groups selected by the vertical motion. l Y

' 38. In a telephone system, a suitable line,

means for preventing seizure of saidline when the same is busy or already in use, an

individual non-numerical trunking switch for said line, trunks to be seized by said switch, a magnet bridged across the line and adapted to initiate the voperation -of said switch when the subscriber calls,- and provisions for making the said magnet unresponsive without opening the bridge whenv the subscriber answers, said sfysteni being operative by vertical motion certain elements thereof to select groups and by rotary motion of the same elements to then connect groups with the called lines found in the selected by the vertical motion.

`39. In a telephone system, a suitable line, means for preventing seizure of said line when 'the same .is busy or already in use, an individual non-,numerical trunking switch for said line, trunks adapted to be seized by saidswitch, and ya. connector for'seizing v said line, said individual switch compris-A ing electromagnet windings bridged across' the said line,"responsive only when the line is calling, and the connector being provided ,l v

with electromagnet windings adapted to be i connected in multiple with the said windings of the individuai switch, Said System A Abeing operative by vertical motion of certainelements thereof to select groups and by rotary motion of the same elements to i' then connectwith-the called lines found in the groups selected bythe vertical motion. 4()` vIn a telephone system, a' suitable line,

means for preventing seizure of said line when the` same lis busy or already in use,

an individual non-numerical trunking switch for said line, trunks adapted' to'be seized by said switch, a connector for'seizing said line, saidvindividual switch comprising electromagnet windingsvbridged across the said Y line responsive only when said line is calling, and the nconnector being provided with electromagnet windings adapted to be .connecte'd in multiple wthithe said windings of the individual switchyjand a common battery ,for geding taglkugggggattlirwsh ,ull of said windings to the said line, Suid.

System being operative by `vcrtical motion of certain elements tluxreoi 4to select groups and by rotary motion of the same elements to vthen connect with the called lines found in the groups selected hy the vertical mo tion.

41. In an. automatic telephone system, means including automatic switches having step-bystep selecting movement Jfor establishing e connection between a calling line and a called line, means common to several subscribers for feeding talking current t'o to several lines Vso the called line, Vand means individual to said called line, connected in multiple with said common 'means, also serving to feed talking current to the said line.

42. In u telephone system,` means including automatic switches having step-bystep selecting movement for establishing a connection between a calling line and n called line, means common to several lines for feeding talking current to a subscribers line, and means indi 'dual 'to that line, con nected in multiple with said common means', also serving to iced talking current te said line.

4:3. In i telephone system, means common to several. subscribers for feeding talking current to the called line. means individual to said culled line, connected in u'ulltiple with' said common means, also serving to iced talking current te the scid line, and subscriberscontrolled means for controlling the circuit of said individual means at the central station.

Liet. In a telephone system, means common for feeding talking current to a subscribens line,4 means individual to that line, connected in multiple with said common means, also serving to feed talkingv current to said line.j and suliscriber-com trolled means 'for controlling the circuit of said individual' means at the Central station, 45. In a telcphoncsystem,a called line,v means common to two or more subscribers for seizing said line, an automatic switch responsive when the said line is 'used as a calling line, but adapted tc remainv normal when the line is call-ed, und means for supplying current through elementswof said switch to the called line for talking purposes. 'i

46. In a telephone system, a called line, an automatic connector common to two or more subscribers or seizing said line responsive to the call, en automatic switch res onsive when the said line used asn cal ing line, but adapted to remain normal when the line is called, and means for. supplying current through elements of sald` automatic switch the called line for talksponsive to a call7 and means for supplyingcurrent through ele ments of sind individual switchv to the called line for tal-king' purposes.

48. In a telephone system, a called line,

a non-numerical trinking switch individual to said line, responsive only when 'the' line calls, means for seizing said line responsive to a call, and mea es for supplying current through elements of said switch to the called line lor `talking purposes. i

49. In telephcne system, a called line, means for seizing said line responsive to the call, means for sending the calling impulses adapted to come ti) rest after each digit, a Vnon-mimerical automatic switch, and means for supplying current through elements of said switch to the 4called line for talking purposes.

50. ln a telephone system, a calling line, a called line, means for sending' the calling impulses adapted '1o come to rest after each digit, means including a switch having both vertical and rotarymotion to extend the call .to the'called line, i non-numerical trunking switch, means fo r supplying current for talking' purposes, connections whereby such current is fed through elements of the firstmentioned switch to the callingl line, and other connections whereby/'such current is fed through elements of said last-mentioned switch to the called line.

5l.` In a teleph )ne system, a called line, means for sending the calling impulses -Jidapted to come to rest after each digit,

'means common to two or more subscribers A and controlled by Said impulses for seizing Athe called line `lor talking purposes, and

means for opening said normal connection when the hneis used as a. calling line.

53. InV a telephone system, means includ-` ing automatic switches for establishing a connection between a calling and a called subscribers line` a normally closed battery bridge across a line adapted to supply current thereto for talking purposes when the line is called, and-means for opening said bridge when the line is used as a calling 54. In a. `telephrme system, e4 normally closed battery bridge acrossv e telephone line adapted@ Supplyllr'rent thereto cr'talking prposes when the line is called, and means responsive to the subscriber of such line'ferppenng said bridge whenthe line is; 'nahe' lmilling line. 2 gln' ul telephone System,means for send- .mjZ-QtheCaIIing impulses adapted to come :im lifter each digit; means individual [t0-g line forlsupplying current thereto for lgalknguilfposes when the'same is used as and.. means common to twg or more subscribers for supplying sucli current to said line when the latter is used as a call.- ing line.

Signed by me at Cl'licago, Cook county, Illinois, 'this 26th day of June, 1907. t

WILSON L. CAMPBELL.

Witnesses:

EDWARD D. FALES, ARTHUR B. SPERRY. 

